Development of plasma electrolytic oxidation for improved Ti6Al4V biomaterial surface properties

In the paper, the scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) results of the Ti6Al4V alloy treated by a novel plasma electrolytic oxidation (PEO) (micro arc oxidation) in the electrolyte containing concentrated phosphoric acid and copper nitrate are presented. The PEO treatment was performed at the voltage of 450 +/- 10 V. The main problem to solve under the experiments was to obtain a porous surface layer composed mainly of titanium phosphates within the copper ions. The performed study has shown that the amount of copper nitrate in 85 % concentrated phosphoric acid should be not less than 1.60 mol/L. The best result in the case of copper (4.3 +/- 0.6 wt%) and phosphorus (19.9 +/- 0.5 wt%) contents in the surface layer was obtained after the PEO treatment in electrolyte with the highest amount of copper nitrate used, i.e., in 3.20 mol/L of Cu(NO3)(2) in H3PO4. Concerning the Ti6Al4V alloy for the use as biomaterial, an interesting characteristic and a great advantage obtained from the proposed PEO treatment is eliminating vanadium and a considerable diminishing of aluminum from the surface coating. Two elements forming Ti6Al4V alloy, vanadium, and aluminum are detrimental for human body. After implantation, vanadium leaking from this biomaterial reveals the carcinogenic effects whereas aluminum has an impact on acceleration and stimulation of Alzheimer's disease. Separation and isolation of the human tissue from the matrix is a crucial task of researchers. The proposed new PEO process fulfills this requirement and may result in great improvement of the biomedical surface characteristics.